More of an opinion that fact i guess. The question refers to ALL libraries/public/school.
Me I have no damn idea. I thought about the bible, but most people own a copy, so no need to check it out.
I actually would bet that it is the Bible or Koran or whatever religious text is popular in your locale.
Going year-by-year, the most popular items are going to be whatever fiction is trending at the time. For a huge number of locales, the most popular item for 2017 was The Girl on the Train by Paula Hawkins.
Looking at the year-by-year lists for the US, if you’re someone who hates Lee Child or James Patterson, you’re going to be disappointed.
In the libraries I’m family with, the Bible, Koran, Book of Mormon, etc. are reference books that don’t circulate. There are dozens of study guides, analyses, interpretations and so on over in Dewey section 200 (Religion) that can be checked out.
“Dr. Spock’s Baby and Child Care”
My guess (I haven’t tried to check) would be What Color is your Parachute. I hear it’s the most stolen book from libraries, so I’d expect it to be legitimately checked out the most, too.
Ironically, I expect that hardly anybody steals the book Steal this Book by Abbie Hoffman*
*There’s no point, anywaty – it’s available free online – Vintage Vinyl:Steal This Book
Praxis Core Study Guide 2018-2019: Praxis Core Academic Skills for Educators Exam Prep and Practice Test Questions is the most frequent and longest waiting list item my library has and it can only be checked out for internal use.
Well, at the Chicago libraries, it’s definitely in circulating, too, around BS185-BS195 (we do Library of Congress here). The problem is there’s so many editions and versions of it, so, depending on the OP’s restrictions, it may not count as a single book.
That said, I only see a handful taken out across the Chicago Public Library system at the moment (maybe about a half dozen to ten. There’s just so many “bible” entries with different editions, translations, etc., that I can’t just pull up all the bibles online and see which ones are checked out. And, yes, I’m looking specifically at bibles, not bible criticism. KJV, Good News, New Living translation, New International edition, versions with and without the apocrypha, etc.)
I work in a public library checking in books that have been returned, and I have only once seen a Bible checked out, and that was in Korean.
Child care books circulate, but not Dr. Spock so much. “What to expect when you’re expecting” is currently more popular.
Our GED test prep books are in use constantly, as are the nurse exam test prep books. There are multiple publishers of those, so it would be hard to point out a specific one.
Jeff Kinney’s “Diary of a Wimpy Kid” books circulate so much that they are worn to a pulp in a few years. We’ve probably purchased 30 or 40 copies of the first one in the 11 years since it was published. I reinforce the corners and spine when we get a new copy in, but they are cheaply constructed and we only get 30 or 40 uses of each one. Demand doesn’t seem to be tapering off over the years, which is what happens to adult best-sellers.
I don’t have access to overall circulation statistics, but those are my impressions of the most checked-out books in my suburban public library branch.